It is known that two or more vehicles moving along a roadway can cooperate as a road train or a “platoon” for mutually providing various efficiency benefits to the vehicles within the platoon. A typical vehicle platoon includes a leader vehicle and one or more follower vehicles arranged serially along a single roadway lane. Larger platoons can involve many follower vehicles for spanning multiple lanes thereby providing enhanced efficiency to more vehicles. However, ensuring the safety of both the platooned vehicles as well as of the other non-platooning vehicles on the roadway usually dictates the short single lane platoon incarnation.
The aerodynamic geometry of a group of vehicles arranged in a platoon provides wind resistance loss benefits superior to the aggregated individual wind resistance losses of the vehicles when travelling separately. A maximum aerodynamic benefit and resultant fuel savings is realized by the vehicles maintaining a small inter-vehicle distance or spacing in terms of reduced energy consumption. However, holding a tight head-to-tail distance or spacing between platooned vehicles requires that careful attention be paid to various functional or environmental and operational characteristics and capabilities of the vehicles and other external conditions including for example the overall size of the platoon, weather conditions, relative braking abilities between vehicle pairs, relative acceleration abilities, relative load or cargo size and weight including required stopping distance, and the like. Special attention must also be paid to characteristics of the roadway such as roadway incline, decline, and turn radii. These various parameters implicate directly or indirectly the inter-vehicle safety considerations as well as the overall safety of multiple vehicle platoons.
In the single lane platoon incarnation described above, the vehicles participating in a platoon typically mutually cooperate to maintain a relatively fixed and constant (even or the same) distance between adjacent vehicles by exchanging deceleration command and other signals between adjacent vehicles of the platoon. On flat roadways, the even distance maintained between the vehicles is often fixed and constant in accordance with control protocols using combinations of global positioning systems (GPS) data sharing, deceleration command signal exchanges, and safety and efficiency algorithms. In any case, the relative distance between the vehicles of the platoon preferably remains substantially even, constant or the same in accordance with platoon control mechanisms and protocols in place.
For maintaining the preferred relatively fixed and constant (even or the same) distance between adjacent vehicles, many commercial vehicles that participate in platoons are highly sophisticated and are also equipped with adaptive cruise control (ACC) systems including forward and rearward sensors used for maintaining a safe relative distance between a host vehicle and a forward vehicle, and collision mitigation (CM) systems for avoiding or lessening the severity of impacts between a host and forward and rearward vehicles using various combinations of transmission, vehicle retarder, and foundation brake controls.
Currently, the technique for vehicles participating in a platoon to share their position with other vehicles of the platoon involves determining, by each vehicle, its own GPS coordinate data, broadcasting by each vehicle its own GPS coordinate data to all of the other vehicles of the platoon using over-the-air communications (such as the J2945/6 communications), and receiving the GPS position data from all of the other vehicles of the platoon. In this way, each vehicle of the platoon knows the position(s) of each other vehicle of the platoon. The GPS coordinate data is then used by each vehicle to, among other things, establish the relatively even distance coordinated between the vehicles as generally described above.
Platooning vehicles follow each other on the roadway in close proximity to each other and often at highway speeds as explained above, and for this they typically use a Radar to control the inter-vehicle distance(s). For emergency braking situations such as Autonomous Emergency Braking (AEB) events for example, forward-directed cameras and/or other sensor(s) on a following vehicle may detect the actuation by a forward vehicle of a rearward facing brake light so that appropriate emergency stopping or other actions can suitably be initiated.
Platoons that operate on public roadways, however, sometimes encounter conditions that require more complicated platoon arrangements and brake monitoring and platooning control and maintenance operations. The close distance between the platooning vehicles poses a risk when the lead vehicle has to decelerate in an emergency situation such as might be required by stopping forward traffic. Therefore in the interest of protecting the platooning vehicles from inadvertent collision with each other, a particular platoon order or arrangement has been devised. More particularly, many platoons are ordered so that the platoon vehicle that is least capable of deceleration is placed at the front of the platoon. This helps to mitigate the chance that the one or more platoon follower vehicles will be unable to adequately decelerate in order to avoid a collision with the platoon leader vehicle. In this platoon topology, the platooning vehicle having the lightest or least braking capabilities or parameters is located at the front of the platoon chain, the vehicle having the highest braking capabilities or parameters is located at the back or rear of the platoon chain, and any one or more intermediate vehicles are arranged from front to back in an order of increasing braking capabilities or parameters. This platoon topology also gives each rearward or following vehicle more time gap for braking in turn relative to the next immediately forward or leading vehicle.
In roadway vehicles, however, braking efficiency is affected by many factors such as brake temperature, brake type, burnishing, vehicle weight, number of tires, tire wear, vehicle loading, road surface type and weather conditions. In addition, the braking efficiency of any vehicle can also change over time, and also can change differently for each vehicle. One or more changes in braking capabilities and any other braking performance characteristics of a first vehicle of a set of platooning vehicles does not necessarily imply that any of the other vehicles of the set of platooning vehicles are experiencing the same one or more changes. That is, one or more changes in braking capabilities of any single vehicle in a platoon cannot reliably be imputed any of the other vehicles of the platoon. This makes management of inter-vehicle gap distances between the platooning vehicles dynamic and therefore more difficult.
Currently towing vehicle safety systems use a “non-enhanced” braking mode when the braking capabilities of the one or more towed vehicles is indeterminate. The non-enhanced braking mode pulses the braking signal from the towing vehicle to the one or more towed vehicles in order to prevent potential instability if the towed unit (or units) does not have functional ABS. The non-enhanced braking mode applies a first level of braking force to the one or more towed vehicles in a predetermined reduced proportion relative to the level of braking force applied to the towing vehicle. This may present a problem for vehicle platooning because sometimes it might be necessary and/or desirable for a following vehicle to apply more braking force to the one or more towed vehicles than the first level of braking force would allow or otherwise permit. This situation could result in potentially less deceleration on the following vehicle which could lead to a collision between the two vehicles.
Given the above, therefore, it will be helpful to provide a system and method to enhance the trailer braking on the following vehicle without the need to know the trailer ABS state, while still minimizing risks.
It would further also be desirable to dynamically adapt the trailer braking strategy for platooning to account for various vehicle and environmental characteristics and performance to maximize equipment value and to enhance the safety of the platooning as well as the non-platooning vehicles.
It would further be desirable to provide a system and method to selectively enhance the braking of the one or more towed vehicles to effect an “enhanced” braking mode, even when the braking capabilities of the one or more towed vehicles is indeterminate, whenever there is a need for braking above a level of braking available in the non-enhanced mode of operation.
It would further be desirable to provide a system and method to selectively enhance the braking of the one or more towed vehicles to effect the enhanced braking mode in response to a deceleration command input having a deceleration command value that is greater than a predetermined threshold deceleration value that is available for operating the combination vehicle in the non-enhanced braking mode.
It would further be desirable to provide a system and method to selectively enhance the braking of the one or more towed vehicles to effect the enhanced braking mode in response to a deceleration command input derived from an operator of the towing vehicle having a deceleration command value that is greater than a predetermined threshold deceleration value that is available for operating the combination vehicle in the non-enhanced braking mode.
It would further be desirable to provide a system and method to selectively enhance the braking of the one or more towed vehicles to effect the enhanced braking mode in response to a deceleration command input derived from a sensor fitted to the towing vehicle for sensing a distance and/or closing between the towing vehicle and one or more forward vehicles, the deceleration command input derived from the sensor having a deceleration command value that is greater than a predetermined threshold deceleration value that is available for operating the combination vehicle in the non-enhanced braking mode.